The idea is simple enough, but this is a short writeup for those who have never changed their manual transmission fluid on the SC300. **NOTE** You CANNOT fill the transmission through the shift hole from inside because the SC300 has an extension on the transmission that brings it back.

Tools needed:

15/16 wrench or 23mm
15/16 socket or 23mm
Ratchet to match
Jack
Jack stands
Funnel with long narrow end
Washer for drain plug and fill plug
2 different sizes of fuel line (One that fits over funnel end and one that fits inside of previous line)
3 quarts of GM Synchromesh (or whatever floats your boat)

Steps:

1. Jack the car up and put on jack stands. Don't forget to chalk the rear wheels with a piece of wood, etc.

2. Whatever you do, for the love of god, loosen the fill bolt first before draining. Use the 23mm or 15/16 wrench (I used a 15/16 because that's what was close and it fit)

3. Drain the fluid into a drain pan and tighten bolt back into place. Replace the washer if necessary.

4. Assemble your funnel/fuel line ghetto transmission filler and run the "filling lines" by the clutch slave cylinder for the shortest route possible.

5. Fill with new fluid. The specs call for 2.7 quarts to fill, but I dumped in all three.

6. Tighten fill plug.

7. Lower car off of jack stands.

8. Enjoy the the newfound buttery smoothness of your shifter.

I hope this helps someone.

-Drake

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i see u guys like to use gm synchromesh, i went to toyota ans got 70/90 like the manual said and i forgot what it said for the rear diff but i did that too, rear diff fluid came out like molasses. is gm synchromesh better ?

why would you go the dealer for gear oil. that a huge waste of money. get gm synchromesh, Schaeffers 267, or redline.

they work well and im sure cheaper then the dealer.

buy things from the dealer when will people learn. our modern society has a thing called the internet and mass communication networks which, with some minor effort, allow you to get a deal on just about anything you will need. im not even talking cars. then again a lot of people are lazy so...eh

you can fill thw fluid on transmissions that are similar to the early r154 and w58. the shifter is internal. on sc300 from 92-94 you can fill it from the shifter. on 95 and up sc300 you cant.

THANK GOODNESS!

I actually did my flush and fill today. DUNKAY owner before me stripped the fill plug as it must have been torqued to 500 ft-lbs. It was not coming off. Popped the shifter assembly out and filled from the shifter hole.

BTW, Redline MT90 FTW! Next up, shockproof for the diff. Used oil reservoir is full so the diff will have to wait.

So i JUST changed the trans fluid on my 92 sc300. I needed a 17mm wrench to take off the fill plug. I tried with the 17 mm socket but when I pulled down it would just slip off the nut, almost stripping it.

Also...the drain plug is NOT 23mm. It is 15/16, like you said, and probably 24mm. If you must buy an extra socket because your set does not have one that big, go with 15/16 because that fits 100% sure on the drain plug. I originally bought a 23mm and it was too small so i had to go back to the store to get the right size. I didnt try 24mm, just went w/ 15/16, but 23mm was JUST too small so 24 would prob work.

Using a 17mm wrench on the fill plug works much better than a socket, so I'd recommend that.

Also, GM Synchromesh is the same thing as Penzoil Synchromesh except for half the price, and you can get it at autozone.

Annnnd lastly, after changing the stinky dark old fluid and replacing it w/ the Penzoil stuff I can honestly say it shifts MUCH MUCH smoother. Almost completely took the little notchiness that I had going from 1st to second away! Its really worth it to change out your old fluid if you havn't before. The drain/fill plug will be quite hard to remove but once you get them started they come right off.